Viscosity changes in ageing unfertilized eggs of Arbacia t)unctulata

In previous studies it was demonstrated that ageing unfertilized eggs of Arbacia punctulata undergo a series of changes including rate of fer tilization, membrane formation, and cleavage (Goldforb, 1918a and b), agglutinin concentration (Goldforb, 1929a and b), and size (Goldforb, in press). Permeability to water and stretching and bursting of the plasma membrane in hypotonic sea water changed markedly with age. These studieswillbe reportedlater. The presentstudy isdevoted to a considerationof the viscositychanges. PROCEDURE Eggs from each female, if in good physiological condition, were washed in 200 cc. sea water. Aliquot portions were transferred to flat finger bowls with 150 cc. sea water. Morning and evening the super natant water was removed, the eggs transferred to clean bowls, and sea water added. Sea water was collected in quantity at high tide, filtered and stored. The pH was 8.3. The temperature in the bowls varied from 18 to 22°C., but during an experiment within 2.5°,usually within 1.5°C. At successive ages eggs from the same bowl were centrifuged by a slightmodificationof the method developed by Heilbrunn (1928). CONSTANT CENTRIFUGAL FORCE, VARYING TIME, EARLY EXPERIMENTS In 1930, ' eggs were centrifuged in 2 mm.-bore tubes in a small elec tric centrifuge. Immediately after centrifuging, the eggs were exam ined in sea water. After preliminary trials a period of centrifugation was chosen that gave the following zonation: (1) Oil cap sharply defined. (2) Hyaline zone in most eggs extended 45 to 55°2 from center of oil cap. (3) Twenty consecutive eggs, with planes of zoning at right angles to the horizontal, were measured. 1 Dr. V. Schechter assisted in these experiments. 2 I.e., degrees on circumference from center of oil cap